Long Ju - Emergent Quantum Phenomena in Graphene

Condensed matter physics aims to explore and understand various quantum phenomena that emerge from the interactions between nuclei and electrons. Through synthesizing and investigating various crystals, this constructionism approach has led to the discovery of many amazing phenomena, especially when the principles of electron correlation and topology play important roles. The settings of such conventional crystals are often very complicated, making it hard to extract the essential ingredients and understand the underlying physics. In this talk, I will show our efforts on establishing a new paradigm, based on a material known as rhombohedral graphene, which is part of natural graphite. Rhombohedral graphene has the simplest chemistry and structure, yet can be controlled by a set of experimental knobs to exhibit many intriguing phenomena in condensed matter physics. Beyond phenomena that were familiar, I will focus on two newly observed quantum phases of matter, chiral superconductor[1] and fractional quantum anomalous Hall effect[2]. I will show their construction, phenomena, and implications for quantum many-body physics and applications. If time allows, I will also discuss our recent work on novel electron crystals in the same material[3]. In the end, I will discuss new opportunities to be explored in this new paradigm.

References:

[1] Han, T., Lu, Z., Hadjri, Z. et al. Signatures of chiral superconductivity in rhombohedral graphene. Nature 643, 654–661 (2025). https://doi.org/10.1038/s41586-025-09169-7

[2] Lu, Z., Han, T., Yao, Y. et al. Fractional quantum anomalous Hall effect in multilayer graphene. Nature 626, 759–764 (2024). https://doi.org/10.1038/s41586-023-07010-7

[3] arXiv:2604.00113